NHC‐Catalyzed Enantioselective [4+3] Cycloaddition of <i>Ortho</i>‐Hydroxyphenyl Substituted <i>Para</i>‐Quinone Methides with Isatin‐Derived Enals

Abstract

Abstract The first enantioselective cycloaddition of ortho ‐hydroxyphenyl substituted para ‐quinone methides has been established by employing isatin‐derived enals as suitable 3C‐synthons under chiral N ‐heterocyclic carbene catalysis. By using this strategy, biologically important ϵ‐lactones have been prepared in good yields (up to 89%) and excellent asymmetric inductions (up to &gt;99% ee, &gt;20:1 dr). Notably, this methodology opens a direct [4+3] annulation entry for the asymmetric synthesis of spirobenzoxopinones bearing an oxindole moiety connected through the spirocenter. magnified image